I. Field of the Invention
The present invention relates generally to trackside railway car handling equipment for positioning railcars along a track for loading or unloading operations. More particularly, the present invention relates to a train positioning system that employs a design that enables it to be operable along a section of curved tracks. The system uses two dog carriages and operates as an indexer against the bogey frames of railcars.
II. Related Art
Freight-hauling railway cars need to be precisely positioned proximate freight or cargo handling equipment during loading and unloading operations. Freight in the form of bulk cargo such as grain is typically loaded or unloaded with reference to stationary freight handling equipment such as chutes and conveyor equipment situated at fixed locations above or in pits beneath a specific portion of the track. Railcars for transporting grain or other such finely divided dry bulk agricultural commodities may be covered and designed with a plurality of spaced bottom discharge hopper bins or chutes accessing the main cargo storage volume. The chutes are closed by capstan-operated rack and pinion bottom closure gate systems.
In the loading and discharge operations, a connected engine roughly positions one end of a string of cars to be loaded or unloaded beneath or above the appropriate equipment at the desired fixed location. Because locomotives are not well suited for precisely positioning individual cars or even strings of cars along a railroad track, positioning devices known as train movers or positioners are located at fixed stations along the track. The positioning devices generally employ heavy pushing members known as railcar-engaging “dogs” to move the cars into position.
Positioning devices are generally classified in the industry as “indexers” or “progressors”. Indexers may employ dogs carried by a pair of carriages operating along indexer tracks on built-in guideways located on the outside of each of the spaced rails of an associated track. Indexers are designed so that the carriages and associate dogs located on both sides of the track are coordinated to operate together in unison to engage and move a car or string of cars along the track. Thus, in indexer type bogey frame-engaging positioning devices, dogs on dog carriages spaced on opposite sides of the track are caused to engage the bogey frame at the same time to thereby provide a balanced force by pushing against both of the spaced sides of the truck bogey frame simultaneously.
Progressors designed to operate against bogey frames also operate along rails in built-in guideways on the outside of each of the spaced rails of a track with dogs that operate along each of the guideways spaced along the track. Rather than operating simultaneously against both sides of a bogey frame to move a car or string of cars, the dogs of a progressor are operated alternately against only one side of a bogey frame, to sequentially engage bogey frames so as to “hand off” the car or string of cars alternating between dogs on opposed sides of the track.
Operation as an indexer advantageously provides a balanced side-to-side force on the bogey frame and enables the total force of two dog carriage systems to be applied at once so that heavier loads may be moved. This also enables a balanced force to be applied against the bogey frames of lightly loaded cars which avoids a possible tipping situation which may occur when force is applied to one side only.
Heretofore, such railcar handling equipment has been constructed to operate only along sections of straight track either as an indexer or a progressor and it would provide a distinct advantage and answer a definite need in the art if such a system could be operated along a curved track section.